Lead-acid batteries conventionally include a multiplicity of cells connected together in series. Each cell consists of a stack of alternating electrode plates, namely cathodes and anodes, each electrode plate having an upstanding lug for electrical interconnection with lugs of similar polarity. Also there is a separator between the electrode plates which prevents shorting of the plates, while allowing ion transport through the electrolyte (generally sulfuric acid). The cells are arranged in a container having partitions that separate adjacent cells. Cast lead connector straps then connect the upstanding lugs from plates of similar polarity in each cell and cast lead intercell connector or straps interconnect adjacent cells in a serial or parallel arrangement.
In the past, as stated above, intercell and terminal connectors or “straps” in lead-acid storage batteries have been formed primarily of castings of lead or of a lead alloy. Lead has predominately been the material of choice for this application for a long time. While lead is not itself a particularly good conductor of electricity, it is inherently corrosive resistant to the sulfuric acid electrolyte contained within the battery. For their relatively low cost, lead-acid batteries provide a modest energy density (the amount of energy produced) per pound of weight, and have a relatively long service life. Other, more conductive metals are either too expensive to be used as the internal connectors in lead-acid batteries, or else they are quickly corroded by the sulfuric acid electrolyte.
For most applications weight is not a factor, and therefore lead is the material of choice for connectors; however, lead is also very heavy, and therefore in applications where weight is a factor, other alternatives have long been sought.
For example, in the aircraft industry, experts have calculated that the fuel cost of flying a commercial airliner is more than $3,000 per year per pound of weight flown. Therefore, if the plane carries batteries having connectors made entirely of led, considerable sums of money could be saved per plane if a lighter weight materials for the connectors could be found.